1. Field of the Invention
The present invention relates to a polypropylene-b-poly(ethylene-co-propylene) or a polyethylene-b-poly(ethylene-co-propylene), and a production process thereof. More specifically, the invention relates to a polypropylene-b-poly(ethylene-co-propylene) or a polyethylene-b-poly (ethylene-co-propylene), that has a superior impact strength and is useful as a compatiblizer for a crystalline polyolefin and an amorphous polyolefin, and a production process of the block copolymer. Furthermore, the present invention relates to a polyolefin material, wherein a polymer in which a polypropylene or a polyethylene and poly(ethylene-co-propylene) are repeated and polypropylene-b-poly(ethylene-co-propylene) or a polyethylene-b-poly(ethylene-co-propylene) are blended in either a polyethylene or a poly(ethylene-co-propylene) or in their mixture.
2. Description of the Related Art
Polyolefins such as polypropylenes and polyethylenes are massively produceed and consumed since they are inexpensive and excellent in processability and various physical properties such as mechanical strength, heat resistance, chemical resistance and electrical insulation. However, for example, polypropylene is poor in impact strength while it is relatively excellent in stiffness; this disadvantage is improved by blending an amorphous poly(ethylene-co-propylene) that is excellent in impact strength. In the conventional block type copolymers, the matrix comprising polypropylene and the domain comprising poly(ethylene-co-propylene) are separated, which causes lowering the physical properties. These problems have been desired to be improved. It is expected that a block copolymer in which a polypropylene and a poly(ethylene-co-propylene) are chemically bonded might overcome these problems and provide a material having more excellent characteristics.
Conventionally, so-called block type copolymers have been known as one type of a polypropylenes that are composed of a polypropylene and poly(ethylene-co-propylene). The conventional block type copolymer is produced by a two-step process comprising, for example, the synthesis of a polypropylene for 30 minutes to several hours in a first polymerization vessel, followed by the synthesis of a poly(ethylene-co-propylene) for also 30 minutes to several hours in a second polymerization vessel. Considering the period of time for forming one polymer chain, chemical bonds between the polypropylene and the poly(ethylene-co-propylene) are not formed in so-called block type copolymers. They exist in a micro-blend state; a true block copolymer as defined in polymer chemistry is not formed, thus satisfactory characteristics as targeted have not always resulted.